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Answer:
The 98% confidence interval for the mean purchases of all customers is ($37.40, $61.74).
Step-by-step explanation:
We have that to find our level, that is the subtraction of 1 by the confidence interval divided by 2. So:
Now, we have to find z in the Ztable as such z has a pvalue of .
So it is z with a pvalue of , so
Now, find M as such
In which is the standard deviation of the population and n is the size of the sample.
The lower end of the interval is the mean subtracted by M. So it is 49.57 - 12.17 = $37.40.
The upper end of the interval is the mean added to M. So it is 49.57 + 12.17 = $61.74.
The 98% confidence interval for the mean purchases of all customers is ($37.40, $61.74).
Answer:
It takes 2.8 seconds for the ball to fall 215 ft.
Step-by-step explanation:
We are given a position function s(t) where s stands for the number of feet the ball has fallen, so we have to replace s with the given value of 215 ft and solve for the time t.
Setting up the equation.
The motion equation is given by
We can replace there s = 215 ft to get
Solving for the time t.
From the previous equation we can move all terms in one side to get
At this point we can solve for t using quadratic formula.
where a, b and c are the coefficients of the quadratic equation
So we get
Replacing on the quadratic formula we get
Using a calculator we get
Physically speaking the only result that makes sense is to move forward in time that give us t = 2.8 seconds.
We can conclude that it takes 2.8 seconds for the ball to fall 215 ft.